Altitude adjustment method and apparatus

ABSTRACT

A portable method and apparatus for allowing an individual to pre-adjust at sea level for future high altitudes is taught. The invention teaches the use of a small portable breathing gas control system to adjust the gas concentrations going to a subject&#39;s facemask.

This application is a continuation-in-part of U.S. Ser. No. 08/927,242filed Sep. 11, 1997 soon to issue as U.S. Pat. No. 5,988,161 which isincluded, by reference, in its entirety.

BACKGROUND OF THE INVENTION

Altitude sickness strikes thousands of individuals every year resultingin problems from sleep disorders to pulmonary edemas to death. Theseindividuals are skiers, mountain climbers, or merely business travelersto high altitude regions. The key to dealing with the altitude sicknessis taking advantage of the body's ability to gradually acclimatizethrough a transition through progressively higher altitudes.

Unfortunately, most individuals do not have the time to acclimatize. Forexample, and individual flying to a high ski hill will typically spend afew hours of flying and driving to be at the ski hill thus depriving thebody of the opportunity to acclimatize.

The physiology of altitude sickness and the adjustment to altitude iscovered in numerous textbooks. An excellent one is “Medicine ForMountaineering” by James Wilkerson, M.D. (Copyright 1992, published byThe Mountaineers of Seattle, Wash.) from which the immediately followingdiscussion is based.

The body adjusts to altitude by increasing respiratory volume,increasing the pulmonary artery pressure, increasing the cardiac output,increasing the number of red blood cells, increasing the oxygen carryingcapability of the red blood cells, and even changing body tissues topromote normal function at lower oxygen levels.

At an altitude level of 3,000 feet the body already begins increasingthe depth and rate of respiration. As a result of this more oxygen isdelivered to the lungs.

In addition, the pulmonary artery pressure is increased which opens upportions of the lung, which are normally not used, thus increasing thecapacity of the lungs to absorb oxygen. For the first week or so, thecardiac output increases to increase the level of oxygen delivered tothe tissues. However, that particular adjustment fades after the firstweek.

The body also begins to increase the production of red blood cells.Other changes include the increase of an enzyme (DPG) which facilitatesthe release of oxygen from the blood and increase the numbers ofcapillaries within the muscle to better facilitate the exchange of bloodwith the muscle.

About 80% of the adaptation is finished by 10 days.

Slowly increasing the altitude from sea level to the target altitudeappears to be the best solution.

The most difficult time for altitude sickness sufferers is evening whenthe primary function is sleeping. This is most likely due to the factthat the breathing rate decreases during sleep and thus the copingmechanism of increased respiratory rate is somewhat thwarted.

Gamow (U.S. Pat. No. 5,398,678) teaches a portable full body chamber tofacilitate the function of an individual at higher altitudes byincreasing the pressure within the chamber above that of the ambient.Lane (U.S. Pat. No. 5,101,819) Kotliar (U.S. Pat. No. 5,799,652) teach ahypobaric chamber to simulate the lower oxygen concentrations at higheraltitudes. Wasastjerna (U.S. Pat. No. 5,860,587) teaches a hypobaricchamber for horses. Kotliar (U.S. Pat. Nos. 5,850833 and 5,924,419) alsoteaches mask based hypoxic short-term (less than one hour) athletictraining devices.

The inventor is not aware of any other art that discusses the use of aportable device for helping an individual to adjust to altitudes whilesleeping.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a subject at rest using the device.

FIG. 2 shows a simple embodiment of the device.

FIG. 3 shows a more complex embodiment of the device.

FIG. 4 shows a method of a simple embodiment.

FIG. 5 shows a method for a more complex embodiment of the invention.

FIG. 6 shows a device exhibiting a simpler embodiment of the invention.

FIG. 7 shows a device exhibiting a simpler embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a subject 10 using the device with mask 12 over the noseand mouth secured around the head by strap 14. The mask communicateswith the main exchange unit 20 through hose 16. For convenience, hose 16should be long enough so that the exchange unit 20 can be far enoughaway from the patients so that it does not interfere with their sleep.However, for optimal performance in air mixing, the hose could be madeshorter to allow for more shallow breaths for the appropriate gaslevels. Alternatively, the exchange unit could be made very small andbuilt into the mask thus obviating the hose 16.

FIG. 2 shows the details of the exchange unit 20 beginning with the hose16 going to the mask. Flexible sides 22 allow for the chamber to expandand contract. Alternatively, flexibility could be gained by the use ofelastic polymers or other materials for the unit surfaces.

Oxygen sensor 24 sits inside the chamber and feeds its signal to acontrol unit 28. The control unit 28 has a setting for an altitude andtime. The control unit then controls the room air solenoid 26 to allowthe passage of room air into the exchange unit when necessary.

The basic operation is rather straightforward. The oxygen sensormonitors the oxygen and controls the room air solenoid. The solenoidwould be open or closed depending upon whether the internal oxygen levelis at that appropriate level desired for the altitude simulation.

More details of this are given in the discussion of the methods, whichare following.

FIG. 3 shows a more complex embodiment of the invention, which adds apressure sensor 40 and CO2 (carbon dioxide) sensor 42 which again feedsinto the control unit 28. This allows for the adjustment of not only theoxygen level but also the CO2 level. It maybe important, for someindividuals, to minimize the level of CO2 as high levels of CO2 caninterfere with breathing reflex.

A second solenoid 44 is used to allow the passage of nitrogen from atank 46 into the chamber. This allows the reduction of oxygen levels inthe chamber without merely increasing the levels of CO2 as occurs withthe simpler embodiment shown in FIG. 2. This further discussion of theuse of this is covered in the following method discussions of FIGS. 4and 5.

FIG. 4 shows the method for a simple embodiment of this invention. Thefirst step is to read the altitude setting on the control unit and toconvert that to a desired oxygen level. The peak oxygen concentration isred by the O2 sensor. This should occur just before inspiration as theexpired air has significantly lower levels of oxygen. If the peak oxygenconcentration (OC) is greater than the desired oxygen concentration(DOC) then the solenoid remains shut. This will increase the level ofcarbon dioxide in the gas chamber and decrease the level oxygen.

If, in the alternative, the peak oxygen level is less than the desiredoxygen concentration then the room air solenoid is open for two secondsto allow fresh air into the chamber to increase the oxygenconcentration.

FIG. 5 shows a more complex embodiment of the invention. The pressuresensor is continually monitored to track inspiration and expiration.This is due to the fact that the inspiration will reduce the pressure inthe tank while the expiration will increase it. Thus the control unit iscontinuously “aware” of the stage of breathing.

As before, the desired altitude setting is converted to a desired oxygenconcentration (DOC). At the beginning of every breathing cycle (or thestart of inspiration) the oxygen level is peak in the exchange box. Thisis referred to as the “O2I”. If the O2I is greater than the desiredoxygen concentration then the method examines the pressure in the box.If the pressure is close to 15 PSI (pounds per square inch- or normalatmospheric pressure) then this means the box has normal pressure andthere is plenty of oxygen so the unit just goes back to monitoring.Eventually, breathing will lower the level of oxygen in the box. If,however, the pressure is not near normal sea level pressure then thenitrogen solenoid is opened for two seconds to increase the gaspressure. (There is no risk of great overpressure, as the mask willsimply allow the excess gas to leak out around the subject's mouth andnose.) After the nitrogen solenoid has been opened for two seconds thenthe CO2 concentration is examined. If this is less than 3% then themethod returns back to monitoring at the top of FIG. 5.

If, however, the CO2 concentration is greater than 3% then the methodopens a room air solenoid for two seconds. This allows in fresh air andwill decrease the CO2 concentration. The step of opening the room airsolenoid for two seconds can also be reached from a negative answer tothe first question. This was “is the O2I greater than the desired oxygenconcentration?” Of the answer was no then it clearly needs to open theroom air solenoid to let in oxygen rich air. After this step then thetimer is examined. If the preset timer has expired then the room airsolenoid is opened permanently to allow the subject to have comfortablenormal breathing. Otherwise the system returns to its normal steps ofmonitoring, etc.

An alternative preferred embodiment is shown in FIG. 6. Here flap valve60 allows the exhaled air to go directly outside of the system. Duringinhalation the flap valve 60 closes forcing the breathing to take placethrough the exchange unit 20. Exchange unit 20 has a disposable screw-incanister 62 of an oxygen absorbent, which reduces the level of oxygen inthe air supplied to the user.

Typical oxygen absorbents are based on a very oxidizable metal. Anexcellent and inexpensive absorber is iron. This can be used very simplyin the form of pellets or powder.

A feature of this invention is the use of “steel wool” for an oxygenabsorber. The “wool” provides high surface area and low breathingresistance. This allows the manufacture of an inexpensive disposablecartridge for consumer use. The oxygen absorbency in increased when theiron oxidation is catalyzed. The iron performance may be improved byhydrogen reduction, electrolytic reduction, or chemical reduction.

Almost any metal can be used but none are as economical and effective asiron. Another feature of this invention is the use of dilute acetic acid(vinegar) as a catalyst for the steel wool.

Other oxygen absorbents include solid electrolyte salts, glucoseoxidase.

The approach of FIG. 6 is not limited to chemical oxygen absorbers. Theelement 62 could just as well be a package of semi-permeable membranefibers, which preferentially leak oxygen out the sides but freely allowthe passage of nitrogen. Representative membranes are composed of4-methyl-penthene-1 with a wall thickness of 12 microns and internaldiameters on the same order.

The system of FIG. 6 offers advantages of simplicity and cost of that ofFIG. 2. There is no need for a valve or other controls. The canister 62merely absorbs oxygen during the user's sleep and stops absorbing whenthe iron is all oxidized. At that point the canister is replaced. Thecanister resistance controls the flow of air and the simulated altitudeof the device. Different canister geometries will simulate differentaltitudes.

It will be appreciated that the oxygen absorber approach could be usedin conjunction with the system of FIG. 3 to replace the nitrogen source46. Instead, room air would be filtered through the oxygen absorber toprovide the nitrogen-rich and oxygen-reduced air.

The device in FIG. 7 is a modification of that of FIG. 2. Themodification is the addition of a disposable carbon dioxide CO2 absorbershown as element 70. While the system of FIG. 2 would work fine to lowerthe partial pressure of oxygen seen by the user, the increase in CO2levels could interfere with sleep. High levels of CO2 cause increasedbreathing volume and eventually leads to psychological discomfort andeven panic.

The O2 sensor 24 and control unit 28 may be dispensed with in thishigher-value system. The geometries of the CO2 canister and the exchangechamber could be merely designed to simulate a fixed 8000 feet foroptimal sleep adjustment.

It may seem paradoxical, at first blush, to attempt to lower CO2 while,at the same time, attempting to lower oxygen levels. However, bylowering both, the relative level of nitrogen is increased. This has thenet effect of lowering the partial pressure of the oxygen.

There are many effective absorbers of CO2 as it is highly reactive. Anymetal hydroxide works well. A very effective one is sold under thetrademark “SodaSorb” by the WR Grace Company. It is a mixture ofsodium-, calcium-, and potassium hydroxide. It is sometime described asbeing primarily sodium hydroxide and calcium oxide. (This distinction isnot critical as the water vapor in the exhalant quickly converts thecalcium oxide to calcium hydroxide.) The carbon dioxide reacts with thehydroxides to form carbonates. Similarly calcium bicarbonate is a veryeconomical CO2 absorber.

Lithium hydroxide is light but more expensive. As a powder it isirritating so it has been used as an impregnate which is processed in aball mill. This is then placed in a semipermeable membrane.

The mineral “ascarite” or soda lime is also used for this purpose.Chlorates, peroxides, and alkali metal superoxides absorb CO2 butgenerate oxygen which defeats the intended purpose of reducing theoxygen levels.

Physical absorbers including activated carbons, zeolites, silicas,aluminas, and ion exchange resins will also absorb CO2.

The CO2 absorber may be mixed with a desiccant such as a silica gel toabsorb exhaled water vapor.

The oxygen absorber 62 of FIG. 6 may also be used with the carbondioxide absorbing system of FIG. 7. This has the advantage of being ableto further lower the oxygen level by increasing the relative percentageof nitrogen entering the chamber 20.

It should be appreciated that the devices shown in FIGS. 6 and 7 allowthe simulation of high altitudes without requiring power compressors orother active components.

A key feature of the high-value embodiment of this invention is abreathing apparatus that may have its disposable components filled bycommon household materials, thus saving significant expense. Otherteachings featured complex high-powered pump driven machines or veryshortacting chemical based systems. The CO2 scrubber chamber 70 isdesigned to be easily removed and refilled with calcium carbonate orsodium hydroxide (lye) and returned to the exchange chamber 20. In thisway, the larger quantities of chemicals that are needed to provide afull night's operation are not prohibitively costly nor does the userhave to stock canisters refills. A refill canister could require between1 and 8 pounds of absorbent for a full night with a typical user.

The oxygen scrubber chamber 62 is designed to be easily removed andrefilled with steel wool moistened with vinegar and returned to theexchange chamber 20. Again, in this way, the larger quantities ofchemicals that are needed to provide a full night's operation are notprohibitively costly nor does the user have to stock canisters refills.

I claim:
 1. A device for acclimating an individual to high altitudeswhile sleeping, said device comprising: a mask for placement on theindividual's face, said mask being arranged and configured to cover atleast the individual's nose and mouth; said mask being soft andcomfortable to avoid sleep interference; said mask having a securementmeans to maintain its position during sleeping; a gas exchange unithaving a fluid inlet and a fluid outlet, said fluid outlet of said gasexchange unit being in bi-directional fluid communication with saidmask; an element to retard the flow of carbon dioxide from the mask intothe gas exchange unit; an element to retard the flow of oxygen into thegas exchange unit; to reduce the level of oxygen contained within saidgas exchange unit to simulate high altitude ambient air while the useris sleeping.
 2. The device of claim 1 in which the element to retard theflow of oxygen contains metallic iron.
 3. The device of claim 1 in whichthe element to retard the flow of oxygen contains steel wool.
 4. Thedevice of claim 1 in which the element to retard the flow of oxygencontains acetic acid.
 5. The device of claim 1 in which the element toretard the flow of carbon dioxide contains a metal hydroxide.
 6. Thedevice of claim 1 in which the element to retard the flow of carbondioxide contains a metal carbonate.
 7. The device of claim 1 in whichthe element to retard the flow of oxygen contains a solenoid.
 8. Thedevice of claim 1 in which the element to retard the flow of oxygencontrols the entrance of room air.
 9. The device of claim 1 in which theelement to retard the flow of oxygen restricts the flow of room air. 10.A device for acclimating an individual to high altitudes while sleeping,said device comprising: a mask for placement on the individual's face,said mask being arranged and configured to cover at least theindividual's nose and mouth; said mask being soft and comfortable toavoid sleep interference; said mask having a securement means tomaintain its position during sleeping; a gas exchange unit having afluid inlet and a fluid outlet, said fluid outlet of said gas exchangeunit being in bidirectional fluid communication with said mask; anelement to reduce the level of carbon dioxide in the gas exchange unit;an element to retard the flow of oxygen into the gas exchange unit; toreduce the level of oxygen contained within said gas exchange unit tosimulate high altitude ambient air while the user is sleeping.
 11. Thedevice of claim 10 in which the element to retard the flow of oxygencontains a solenoid.
 12. The device of claim 10 in which the element toretard the flow of oxygen controls the entrance of room air.
 13. Thedevice of claim 10 in which the element to retard the flow of oxygenrestricts the flow of room air.
 14. The device of claim 10 in which theelement to reduce the level of carbon dioxide in the gas exchange unitcontains a metal hydroxide.
 15. The device of claim 10 in which theelement to reduce the level of carbon dioxide in the gas exchange unitcontains a metal carbonate.
 16. The device of claim 10 in which theelement to reduce the level of carbon dioxide in the gas exchange unitcontains ascarite.
 17. The device of claim 10 in which the element toreduce the level of carbon dioxide in the gas exchange unit containsactivated carbon.
 18. The device of claim 10 in which the element toreduce the level of carbon dioxide in the gas exchange unit containszeolite.
 19. The device of claim 10 in which the element to reduce thelevel of carbon dioxide in the gas exchange unit contains a silica. 20.The device of claim 10 in which the element to reduce the level ofcarbon dioxide in the gas exchange unit contains an alumina.
 21. Thedevice of claim 10 in which the element to reduce the level of carbondioxide in the gas exchange unit contains an ion exchange resin.
 22. Amethod for acclimating an individual to high altitudes while sleeping,said method comprising the steps of: placing a soft and comfortable maskon the individual's face, arranging said mask to cover at least theindividual's nose and mouth; securing said mask to maintain its positionduring sleeping; connecting a gas exchange unit having a fluid inlet anda fluid outlet, said fluid outlet of said gas exchange unit being inbidirectional fluid communication with said mask; reducing the level ofcarbon dioxide in the gas exchange unit; retarding the flow of oxygeninto the gas exchange unit; thus reducing the level of oxygen containedwithin said gas exchange unit to simulate high altitude ambient airwhile the user is sleeping.
 23. The method of claim 22 in which the stepof retarding the flow of oxygen uses a solenoid.
 24. The method of claim22 in which the step of retarding the flow of oxygen controls theentrance of room air.
 25. The method of claim 22 in which the step ofretarding the flow of oxygen restricts the flow of room air.
 26. Themethod of claim 22 in which the step of reducing the level of carbondioxide in the gas exchange unit uses a metal hydroxide.
 27. The methodof claim 22 in which the step of reducing the level of carbon dioxide inthe gas exchange unit uses a metal carbonate.
 28. The method of claim 22which the step of reducing the level of carbon dioxide in the gasexchange unit uses an ascarite.
 29. The method of claim 22 in which thestep of reducing the level of carbon dioxide in the gas exchange unituses activated carbon.
 30. The method of claim 22 in which the step ofreducing the level of carbon dioxide in the gas exchange unit useszeolite.
 31. The method of claim 22 in which the step of reducing thelevel of carbon dioxide in the gas exchange unit uses a silica.
 32. Themethod of claim 22 in which the step of reducing the level of carbondioxide in the gas exchange unit uses an alumina.
 33. The method ofclaim 22 in which the step of reducing the level of carbon dioxide inthe gas exchange unit uses an ion exchange resin.